A Roche blood test to screen fetuses for Down syndrome worked far better than standard prenatal screening tests in younger, low-risk women, US researchers said on April 01, setting the stage for more widespread use.
The new study, published in the New England Journal of Medicine, is the largest to show the tests are accurate in even low-risk women. But experts warned that women who test positive still need to confirm the result through more invasive diagnostic testing such as amniocentesis, especially if they would consider terminating a pregnancy. "This is a great test for detecting Down syndrome but it doesn't detect everything, it isn't diagnostic, and it doesn't always work to provide a result," said Dr Mary Norton of the University of California, San Francisco.
Prior studies have shown such fetal DNA tests, which measure DNA fragments from the placenta circulating in the mother's blood, are highly accurate at detecting Down syndrome and two other chromosomal abnormalities in high-risk women, typically those over the age of 35.
Several physicians' organisations have supported use of the newer cell free fetal DNA tests over the standard screening in older, high-risk women.
Norton and colleagues tested nearly 16,000 women who had an average age of 30. The researchers compared Roche's Harmony test to standard prenatal screening for Down syndrome - which relies on biomarkers in the blood and a fetal ultrasound - in the same group of women.
The Roche test identified all 38 cases of Down syndrome compared with 30 detected by standard screening. The false positive rate for the new fetal DNA test was 0.06 percent of the study population versus 5.4 percent for standard screening. But there were still nine false positive results in the group that got cell free fetal DNA screening.
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